radix_sort.cpp

// Radix Sort

#include <iostream>
using namespace std;

// Function to get the largest element from an array
int getMax(int array[], int n)
{
    int max = array[0];
    for (int i = 1; i < n; i++)
        if (array[i] > max)
            max = array[i];
    return max;
}

// Using counting sort to sort the elements in the basis of significant places
void countingSort(int array[], int size, int place)
{
    const int max = 10;
    int output[size];
    int count[max];

    for (int i = 0; i < max; ++i)
        count[i] = 0;

    // Calculate count of elements
    for (int i = 0; i < size; i++)
        count[(array[i] / place) % 10]++;

    // Calculate cumulative count
    for (int i = 1; i < max; i++)
        count[i] += count[i - 1];

    // Place the elements in sorted order
    for (int i = size - 1; i >= 0; i--)
    {
        output[count[(array[i] / place) % 10] - 1] = array[i];
        count[(array[i] / place) % 10]--;
    }

    for (int i = 0; i < size; i++)
        array[i] = output[i];
}

// Main function to implement radix sort
void radixsort(int array[], int size)
{
    // Get maximum element
    int max = getMax(array, size);

    // Apply counting sort to sort elements based on place value.
    for (int place = 1; max / place > 0; place *= 10)
        countingSort(array, size, place);
}

// Print an array
void printArray(int array[], int size)
{
    int i;
    for (i = 0; i < size; i++)
        cout << array[i] << " ";
    cout << endl;
}

// Driver code
int main()
{
    int array[] = {121, 432, 564, 23, 1, 45, 788};
    int n = sizeof(array) / sizeof(array[0]);
    radixsort(array, n);
    printArray(array, n);
}